This invention relates to a refrigerated display cabinet having improved refrigerating means.
Refrigerated display cabinets which have a front opening and multiple air curtains to isolate the refrigerated space from ambient atmosphere are well known. With this type cabinet, the refrigerated foods or other merchandise can thus be easily removed from or placed in the refrigerated space.
Such cabinets have gained wide acceptance in the food industry. Air to provide an innermost curtain and at least one adjacent outer air curtain is normally circulated through conduits provided within the display cabinet. The innermost air curtain is normally the coldest and the second curtain somewhat warmer. A refrigerating means, normally having one or more evaporators, is located in the innermost curtain conduit for cooling the air.
In this type of refrigerated display cabinet, the innermost curtain conduit and refrigerating means must be defrosted to remove accumulated frost collecting on the evaporators from the circulating air which tends to impede the operation of the equipment. Commercially, such defrosting operations have been achieved with electrical heaters adjacent to the evaporator of the refrigerating means. However, with electrical heater defrosting, the refrigerating operation has to be temporarily heated while still allowing air to continue circulating. Thus, the circulating air is warmed by the high voltage electrical heater. This warm air can then melt frost built up on the evaporator. It is important to melt this frost as rapidly as possible in order to minimize temperature rise of the refrigerated goods and to minimize collection of frost on the refrigerated goods derived from the higher humidity in the recirculated warm air.
One solution to resolve the above mentioned disadvantages is the use of two evaporators through which the refrigerant is passed, respectively, i.e., the refrigerant flows into one of the two evaporators to function in refrigerating the circulating air while the remaining evaporator is stopped to promote the defrosting operation. The flow path of refrigerant to the evaporators is controlled by the frost build up situation on the evaporators. Thus, the refrigeration of the circulating air is continued to maintain the temperature in the refrigerated space of the display cabinet.
However, if two evaporators are disposed parallel to each other within the display cabinet while still maintaining the outer size configuration of the display cabinet then the display space for merchandise within the cabinet is reduced. Conversely, if the display cabinet outer dimensions are maintained along with the desired original size display space and still two evaporators are provided, then the size of the evaporators, i.e., heat transfer area of the evaporators, must be reduced. As a result of reduction of the heat transfer area, the refrigerating means operates with reduced evaporating temperature within the evaporators. Therefore, the refrigerating capacity requirements are increased and the amount of frost build up on the evaporator is increased. Also refrigerant tends to collect in the evaporator during lower load operation of the refrigeranting means.